Genetics Northern California

Maternal Age Risks

Although it is possible for a woman of any age to have a baby with a chromosome abnormality, the chance increases as you age. Screening tests, such as serum integrated screening, sequential integrated screening, and quad screening, consider your age when estimating the chance for you to have a baby with a chromosome abnormality. This means that the chance for you to receive a "screen positive" result increases as you get older.

The following chart shows the approximate chances of having a baby with any chromosome abnormality, and the chance for Down syndrome:

 Mother's age at
Due Date

Approximate chance for any chromosome abnormality at birth

Approximate chance for Down syndrome at birth

 

15

1/450

1/1000

16

1/475

1/1100

17

1/500

1/1250

18

1/525

1/1425

19

1/550

1/1650

20

1/525

1/1650

21

1/525

1/1650

22

1/500

1/1650

23

1/500

1/1425

24

1/475

1/1250

25

1/475

1/1250

26

1/475

1/1100

27

1/455

1/1000

28

1/435

1/1000

29

1/420

1/900

30

1/385

1/900

31

1/385

1/800

32

1/325

1/725

33

1/285

1/600

34

1/250

1/465

35

1/200

1/365

36

1/165

1/285

37

1/125

1/225

38

1/100

1/175

39

1/80

1/140

40

1/65

1/110

41

1/50

1/85

42

1/40

1/65

43

1/30

1/55

44

1/25

1/40

>45

1/20

1/30